This invention relates to an artistic technical knife, having an extendible and retractable blade that is suitable for cutting paper and other materials.
The prior art artistic technical knife, as shown in FIG. 1, comprises a sectional and frangible blade 1 inserted in a holder 2. The prior art blade is single-edged, that is, only one edge is sharpened. To extend or retract blade 1 from holder 2, a push knob 3 attached to blade 1 is moved to the left or right. To use the knife, the end of blade 1 is extended from holder 2. When the cutting edge of the blade becomes blunt, a section having the shape of a parallelogram at the end of the blade is broken along a frangible recess or weakened line 6 so that a new cutting edge becomes available. The prior art artistic technical knife wastes a significant portion of the blade. Since the blade is typically made of an expensive steel alloy, it is wasteful to discard a whole parallelogram-shaped section of the blade when the cutting edge becomes blunt. Also, it is time-consuming and troublesome to frequently replace the used-up blade with a new blade.
One solution to the problem would be to shorten the distance between frangible recesses. However, if the distance is too small, it is difficult to break a single section. Instead, two or more sections are broken at one time. In practice, the distance between two such frangible recesses on the blade of the prior art artistic technical knife is the shortest possible. However, such knives still waste a significant portion of the blade.